Cellulose vs. Fiberglass Insulation

While fiberglass insulation remains popular, homeowners should consider cellulose insulation for their next home improvement project. Not only is cellulose insulation a sustainable material, but it can save up to one fifth of the energy costs when compared to fiberglass. And although it may be more difficult to install, cellulose insulation offers several advantages that make it worth a look.

Image Courtesy Cellulose.org

R-value is King

Although cellulose insulation has a very slight advantage in R-value per square inch of material when compared to fiberglass, the real gains go beyond a single number. Perhaps the largest advantage of cellulose insulation is its ability to eliminate gaps between the insulation and wall. These gaps are often a large source of energy loss, and one that fiberglass insulation cannot easily address.

In fact, some studies indicate that cellulose insulation can prevent 20% more energy loss than fiberglass due to its superior ability to reduce air infiltration.

Studies have also indicated that fiberglass insulation loses its R-value as the outside air gets cooler, while cellulose shows little change [source]. This makes cellulose insulation a great choice in climates where extreme cold is common.

Which Type Wins the Embodied EnergyCategory?

Fiberglass has a higher embodied energy than cellulose. Fiberglass insulation is created by melting glass and spinning it into thin insulating fibers. It is often made of new materials, and rarely incorporates recycled products.

Cellulose insulation requires none of these high embodied energy materials. Instead it uses recycled newspaper for the bulk of the material. In order to be fire retardant, borox must be added, however, the energy required to mine the borax is still far less than the amount required to produce fiberglass insulation [source].

Off gassing, fire, and health concerns

Many homeowners’ largest concern about cellulose insulation is its flammability. Although the newspaper contained within the insulation is flammable, cellulose insulation is treated with borax and must pass stringent fire safety tests. Some manufacturers claim the cellulose insulation, once installed, is even less flammable than fiberglass because it prevents fire from having access to oxygen.

Fiberglass insulation isn’t flammable, but the formaldehyde glues that are used to create it can pose a significant hazard. Not only is off-gassing a problem, but the formaldehyde glues can create noxious fumes if your home ever catches on fire.

Even without the formaldehyde glues, some studies have shown that fiberglass could be a carcinogen [source]. This concern seems to center primarily around fiberglass that becomes air born, usually through the installation process. For this reason, some companies sell fiberglass that is encased in kraft paper and plastic.

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